The present invention relates broadly to internal combustion engines, and more particularly to an arrangement for varying the effective length of the drive shaft moment arm of the crank shaft assembly to maximize torque output for a given combustion chamber volume.
Internal combustion engines were invented in the 1850's and were first placed in practical use by Nicolaus Otto sometime thereafter. In 1885, the first automobile to utilize an internal combustion engine was built by Karl Benz, who received a patent for his invention in 1886. Production vehicles based on this design were first sold in 1888, and the automobile industry was borne.
Since then, automobile manufactures have developed their engines with an emphasis on producing greater power and durability. In the 1950's, the trend was to use large engines and to maximize those engines for greatest (higher) torque, particularly in the United States and other areas outside of Europe. However, these engines have proven to be terribly inefficient.
This was particularly problematic in the 1970's during gasoline rationing attendant to the 1973 oil crisis and 1979 energy crisis. From approximately that point forward, automobile manufacturers and legislatures began focusing more attention to engine efficiency and initiated greater emphasis on designing more powerful engines that use less fuel.
Early advances were in the form of fuel injection systems which developed to efficiently utilize every ounce of available gasoline. These injection systems featured pumps adapted to push fuel under pressure through a small orifice, atomizing the gasoline particles, and replaced the conventional carburetor which relied on vacuum created by the air intake to supply fuel. With the advance of fuel injection, fuel input could be more accurately regulated. By the late 1980's, virtually all new automobiles featured fuel injection rather than carburetors.
Material science advances also permitted more fuel efficient engine designs. Such designs featured more durable wearing components, such as valves, and lighter components, such as alloy pistons. These advances improved engine efficiency drastically and permitted use of faster reciprocation and overhead cams. Nevertheless, the basic operation of the engine did not change.
In this regard, it is well known that internal combustion gasoline engines utilize a mixture of air and gasoline which in conjunction with a spark ignite to produce power over a stroke pattern, often identified as intake, compression, combustion, and exhaust. In these engines, the piston(s) reciprocate between a top dead center (TDC) position and a bottom dead center (BDC) position. The distance the piston travels between the TDC and BDC positions is referred to as a stroke length.
A four stroke engine requires four piston strokes, or two full revolutions of the drive shaft, to complete one cycle while a two stroke engine requires only two piston strokes, or one full revolution of the drive shaft to completely one cycle. For purposes of this invention, the engine may be either two or four stroke. However, the discussion will generally focus on a four stroke engine as such are more popular than the increasingly unpopular two stroke variety.
During the first stroke of a four stroke engine, the piston recedes from TDC to BDC and the intake valve (or valves, as the case may be) opens to permit air into the combustion chamber, which is mixed with an appropriate amount of gasoline through the fuel injector. In the second stroke, the intake valve closes and the piston compresses the mixture as it moves back to TDC. Combustion starts as the piston passes TDC in the third stroke in response to a spark produced by the spark plug. As the reaction starts, atom by atom the temperature and pressure of the mixture raises drastically. Reaction takes place in a very fast manner, and it may be observed as an explosion. As the piston passes TDC a few drive shaft degrees, most of the fuel inside the chamber has been consumed and the highest temperature and pressure has been achieved. The attendant increase in volume as the piston moves toward BDC causes the gas to start loosing its pressure while the crank shaft assembly keeps moving to a higher moment arm position. The pressure of the gas influences a moment to the drive shaft with the help of the piston and the connecting rod to produce power. As the piston passes the BDC position, the exhaust valve (or valves, as the case may be) opens and exhausted gases leave the combustion chamber, thus completing the fourth cycle. As the piston again passes through TDC in the fourth cycle, the first cycle begins again.
Taking a non-adiabatic view, the conventional engine of this type includes two parameters that influence only torque, one is the pressure (P(y)) and the other is the length of the moment arm. The following equation mathematically describes the physical parameters of the engine.Radius=moment arm=piston rod length=stroke length/2
And the torque of a motor is defined as:
T(x,y)=P(y)*Apiston*x at a given (x,y) point of the piston rod pin center line.
x is defined as R*sin(θ), where θ is the angle between center of piston rod pin and the 0 point.
As more fuel and air is delivered into the cylinders, P(y) increases automatically. However, to manufacture an efficient engine, one endeavors to use less fuel for a given power output. Thus, it would be advantageous to devise an engine having increased torque while at the same time consuming less fuel.